Direct LAMP assay from clinical sample for carbapenem resistant A. baumannii

Carbapenem-resistant Acinetobacter baumannii (CRAb) is one of the most important nosocomial pathogens and provokes various infections such as ventilator associated pneumonia (VAP) in ICU. For prevention of VAP by CRAb, rapid and sensitive diagnostic technique for this pathogen is indispensable. The aim of this study is to evaluate how useful the CRAb LAMP (Loop-Mediated Isothermal Amplification) assay which we developed is in clinical practice, and to compare the detection rate between sample collection sites; bronchial aspirates and rectal swab. Samples were collected from the intubated patient in the ICU of university hospital in Bangkok, Thailand. Our CRAb LAMP assay can use clinical specimens directly as the template of LAMP reaction and detects CRAb by amplifying blaOXA-23 gene, which is highly conserved among CRAb isolates in Thailand. The CRAb LAMP provides the result within 40 minutes from sample collection and can be used for active surveillance. Our CRAb LAMP has high sensitivity (100% (31/31)) and high specificity (84.1% (74/88)) enough to apply to clinical setting. Furthermore when the results of CRAb LAMP in each site were compared, 92.5% of them were concordant each other. These results suggested that our CRAb LAMP effectively detect CRAb in bronchial aspirates. Moreover the CRAb LAMP from rectal swab is a useful method for detecting CRAb-positive patient and can be used as the active surveillance for CRAb, since collection of rectal swab is easier and accomplished in all cases. To reduce the number of VAP patients, detection of CRAb is the first and necessary step. Our CRAb LAMP assay must be applied as a diagnostic test to detect carriages of CRAb.